Machine for grinding gears



Dec. 4, 1928. 1,693,781

. B. w. HANSON MACHINE FOR GRINDING GEARS Filed NOV. 16, 1923 4 Sheets-Sheet 1 WmuwbW I Dec. 4, 1928.

B. M. w. HANSON MACHINE FOR GRINDING GEARS Filed Nov. 16, 1923 4 Sheets-Sheet I 2 llll a v a 1 KM m a w 6 k w 8 W W w f a w J Dec. 4, 1928.

1,693,781 B. M. w. HANSON MACHINE FOR GRINDING smas- Filed Nov. 16, 1925 4 Sheets-Sheet 5 mm: 6 6!. 75 m 77 .107 6 I 1/ Jar Lmb 1a! mm,

1 1 2a lllllllHRk :i i ii .52 {:31} a H H 2| a1 I gvvumlhn Dec. 4, 1928. 1,693,781

B. M. W. HANSON 'MACHINE FOR GRINDINGGEARS Filed Nov. 16, 1923 4 Sheets-Sheet 4 Quorum:

Patented Dec. 4, 1928.

UNITED STATES PATENT OFFICE. I

BENGT M. W. HANSON, OF HARTFORD, CONNECTICUT; EINAR A. HANSON EXECU'IOR OF SAID BENGT M. W. HAN SON, DECEASED.

MACHINE FOR GRINDING GEARS.

Application filed November This invention relates to metal working machines, and has particular reference to machines for grinding toothed gears and the like.

The. general aim of the invention is to provide an improved machine by means of which the teeth of gears, and the like, may be expeditiously and economically ground with precision.

in accordance with the presentinvention, the machine is provided with an abrasive. screw, the thread ol which has a pitch c0rresponding to the. circular pitch of the. gear to be. ground. The abrasive screw and gear blank, while in mesh, are rotated at such relative speeds that the thread on the abrasive screw will generate the proper curve of teeth on the-gear. With this arrangement, a plurality of eonvolutions of the thread on the. abrasive screw are operating at the same time to grind the gear blank, thus etl'ecting rapidity in the grinding operation and, since wear upon the grinding medium is distributed along a number of convolutions thereon, the abrasive screw will have a lon or life and will require truing up at less requent intervals. For the purpose of further increasing the eflieiency and accuracy of the machine to the extent that the abrasive screw may be used'for longer length of time without retruing, and errors due to wear of the abrasive screw are reduced to a minimum, the arrangement is such that the abrasive screw may be moved axially, thus changingor shifting the grinding areas of the thread thereon, without, however, disturbing the operative relation between the abrasive screw and gear blank. Preferably, the abrasive screw and gear blank, particularly where spur gears are ground, are relatively moved axially of the gear blank in order to grind the gear teeth throughout their lengths, i. e., throughout the thickness of the gear, and where spiral toothed gears are ground, the rotation of the gear blank is modified in accordance with the angularity of the teeth so that. as the gear is moved axially, the teeth thereof will be in proper mesh with the thread on the abrasive screw. A further object of the invention is to provide a machine of this sort with means for accurately forming and truing the spiral rib 16, 1923. Serial No. 675,034.

strued as a limitation of the scope of my invention. Quite obviously, the machine and the methods carried out by the use thereof are susceptible of various forms, modifieat-ions and changes, and for this reason I the maehine shown in the accompanying drawings is illustrated more or less diagrammatically or conventionally.

The invention accordingly consists in the features of c mstruetion, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the application of which will be indicated in the appended claims.

In the accompanying drawings:

Figure 1 is a front elevational view of the machine;

Fig. 2 is a view looking at the right hand side or end thereof;

Fig. 3 is a view looking at the other end;

Fig. 4 is a view looking at the truing machine from the front, this view being taken substantially on line 44 of Fig. 3;

Fig. 5 is a detail view showing the cam by means of which the abrasive screw is withdrawn from operative position; a

Fig. 6 is a partial sectional View through the abrasive screw mounting. being taken substantially on line 66 of Fig. 1; i

Fig. 7 is a top plan of the truing mechanism;

Fig. 8 is a view, of a more or less diagrammatic nature showing a trning mechanism for dressing the thread of an abrasive screw to be employed for finishing double curve gear teeth, for instance; and

Fig. 9 is a detail view showing the manner in which the lever 33 may be pivotedly mounted.

Referring to the drawings in detail, a is suitable construction. bis the'spindle on w oh the abrasive screw c is mounted,-'and d is a vertical work carrying element'or spindle, here shown as carrying a straight spur gear blank e. The grindi element or abrasive screw 0 is of cyhn-' drical form, being, preferably, constructed of emery or the like, and'has upon its periph ery an integral spiral rib or thread which is preferably continuous from end to end.

The thread-on the abrasive screw is preferably of uniform outside diameter and uni-. form root diameter throughout its length. The thread of the abrasive screw will be of such pitch and shape in cross-section that the screw, in outline,

with the gear operated upon. The work spindle is properly connected up to the abrasive screw sp ndle, so that they are driven at the proper relative speeds, and the driving connections of the spindles, as hereinafter described more in detail. The letter f designates, generally, the mechanism for truing or resurfacing the thread on the abrasive screw.

It may be here stated that the work is shown, by way of example only, as a spur gear having straight teeth; that the work spindle is described as being vertical, and the a rasive screw spindle as generally horizontall disposed, but it is not intended to limit t e invention to this. specific arrangement, the terms vertical and horizontal" being employed merely for. convenience in explaining the relative position of the parts;

and, in some instances, either the abrasive screw spindle or the work spindle may be moved, one relative to the other, to accomplish the desired result as, for instance, in place of moving the work spindle vertically to effect cutting of the gear'teeth throughout their length, the abrasive screw may be fed downwardly on a line in parallelism with the axis of the work. Other reversals of parts and changes will be obvious.

In accordance with the present illustrative and somewhat diagrammatic disclosure .of the invention, the to of the bed a is rovided with ways 10 on which is mounted, or movement towards and away from the axis of the work spindle, a two-part carriage including a main slide 11 and a supplemental slide 11. The latter slide has, at its forward end, an upstanding arcuate segment or guide 12 sup porting, for angular adjustment, a slide 13 which carries a holder or bearing member 14 in which the tool spindle b is ournaled. Movement of the carriage is controlled by a cam 15 (see Figs. 1 and 5) which is of such construction and so connected up to the work spindle and abrasive screw, that the abrasive screw is moved into operative relation to the gear blank and held in this position durin the grinding plane," will correspond to a rack adapted to mesh may include 'means for changing or modifying. the speed of rotation I the grinding operation, and then moved out (if-operative position after the grinding operation ,hasbeen completed to permit the gear blank to 'clear the abrasive screw when the gear blankis lowered or moved on its reverse or inoperative stroke. The supplemental slide 11 is adjustable on the main one 11 of a screw 16, so as to properly osition the abrasive screw transversely o .t e work or bring it into proper relation to the truing device. The segment or guide 12 supports the tool or spindle for angular adjustment about an axis or line assing diametrically through the axis of t e abrasive screw in order to permit the abrasive screw to be brought into proper relation to the work, for instance, to ring the screw into inclined position corresponding to the lead of the thread of the abrasive screw, where a spur gear with straight teeth is being ground, or in accordance with the lead of t e thread on the abrasive screw and the angularity of the teeth, where a spiral toothed gear is to be operated upon. The support or slide 13 may be secured in any angular position of adjustment on the guide 12 in any appropriate manner, as by means of a clamp 18.

In accordance with the present invention, the arrangement 'is such that the gear operated upon and the abrasive screw may be relatively moved during the grinding operation, preferably without disturbing the operative relation therebetween, in order to change-or shift the effective grinding area of the threadof the abrasive screw; that is to say, the parts are relatively moved in such manner that successively new grinding surfaces on the thread of the abrasive screw are brought into play, whereby wear on the screw is distributed, thus giving to the screw a longer life and making for efficiency in that the screw need be trued up at less frequent intervals. .The diameter of the abrasive screw selected will depend upon a number of factors but, refe'rably, the size of. the screw will be suc that the gear being ground will be rotated during the grinding operation, to bring its successive teeth into operative relation to the abrasive srrew, at a maximum speed consistent with that peripheral speed of the abrasive screw which is most efiective in grinding. It will be understood that, irrespective of the diameter of the abrasive screw, if it is provided with a single thread, upon each revolution thereof the gear operated upon is turned through the distance of its circular pitch. If an abrasive screw of suchlarge diameter is selected that,

while maintaining the most efi'ective grind-- in any suitable manner, as by means ill) screw will be made of smaller diameter, so

that it may be rotated at-the most effective cutting speed with that convolution or those convolutions thereon in engagement with a larger one if the two screws are driven at the same peripheral speed, and, therefore, in a given period of time, the smaller abrasive screw will take more cuts on the gear operated upon, which means. that the grinding operation may be carried out with greater rapidity. However, where a smaller abrasive screw is used, should it not be shifted so as to change the grinding areas thereon, wear on the screw would be greater than would be the case if a larger screw were employed and more frequent truing up of the screw would be required. In order to avoid this, I propose to employ an abrasive screw of such a diameter as to give the most effective results, and shiftthe same axially so as to change the grinding areas of the convolutions thereon, thereby distributing the'wearon the several convolutions. abrasive screw will be of such length as to permit it to be shifted axially to the desired extent In the. drawings I have shown the abrasive screw as being, say, twir'e as long as would be necessary if the screw were not shifted axially. In the present illustrative disclosure axial shifting movement of the. abrasive screw is provided by mounting the holder 14 for sliding movement in the support 13 and moving the holder in any appropriate manner as by means of a lead screw 17 which is connected up to the drive mechanism for the tool and work spindles so as to be driven in proper timed relation thereto. It will be observed that, irrespective of the angular adjustment of the abrasive screw, the grinding plane or line on which the grinding operation is carried out is notehanged or varied; that is to say, the abrasive s"rew may be moved axially without disturbing the operative relation between the abrasive screw and the work.

On the forward face of the bed a; are suitable longitudinally extending ways 20 on which is slidably mounted a work carriage or slide 21 having a vertical bearing portion 22 in which is journaled, against axial movement, a sleeve 23. Vertically movable in this sleeve, but keyed against rotation relatlve thereto, is the work supporting element or spindle d. The mounting of the work spindle'on the slide 21 may be found to be of advantage in properly adjusting the work so that the'teeth thereof will mesh with the thread on the abrasive screw. The slide 21 may .be adJusted in any approved manner as, for instance, by means of a screw 24.

'On the lower end of the sleeve 23 is fixed a worm wheel 25 with which meshes a worm The 26 carried by the slide 21 and splined ona shaft 27, which shaft is connected up with the abrasive screw spindle through suitable change gears and compensating meehauisi-u, as hereinafter described more in detail.

In order that the gear teeth will be properly ground throughout-their length, the work spindle d is slowly raised during the grinding operation and then uickly returned to starting position after tl screw has been moved back out of the way and the grinding operation has been completed. This reciprocating movement of the 'work spindle may be accomplished in any suitable ordesired manner, but by way of ex-. ample I have shown a cam for this purpose, this cam being operatlvely. connected to the drive mechanism for the work and tool spindles. The lower end of the work spindle d rests upon a plunger 31 having a rearwardly extending pin 32 straddled by the bifurcated end of a lever 33 adjustahly pivoted, as at 34, and having on its other end a roller 35 engaging the periphery of the cam 30. It will be seen that when the cam 30 is rotated in a clockwise direction, the plunger 3l,together with the work spindle d resting thereon, is gradually raised until the high point of the cam passes from beneath the roller 35, when the work spindle and plunger 31 will drop back under their own weight to starting position. Preferably, the lever 33 is adjustably pivoted to the frame a, and, to this end, the pivot pin or stud 34 extends through the elongated opening 36 in the lever. By adjusting the pivot 34 for the lever '33, the extent of travel and the speed of the vertical movement of the work spindle will be varied. For instance, it the pivot 34, which is in the form of a bolt having a head engaging in a T-slot 37 (see Fig. 3), is adjusted to the left, the extent of vertical movement ofthe spindle (I will be lessened and the speed with which it is raised is slower.

It is, of course, understood that the work spindle and the abrasive screw spindle may be rotated through any suitable driving mechanism, but, by way of example, Iliave shown one arrangement which may be. adopted. For instance, a drive pulley 40 may bemounted on the outer end of the abrasive screwspindleb. Carried by this spindle is a worm 41 meshing with a worm wheel 42 fixed on a shaft. 43' journaled in a bearing 44 provided on the holder 14. Journaled in suitable hearings on the side of the bed a is a shaft 45 connected by gears 46 to astud shaft 47 which, in turn, is connected to the shaft 43 by an extensible shaft 48. The shaft 48 is connected to the shaft ie-abrasi ve flu the shaft 45 through suitable compensating mechanism including on the work, where a spiral toothed gear is to be operated upon, this being necessary be cause. in the grinding operation, the gear is raised so as tobring successive longitudinal portions of its teeth into engagement with the abrasive screw, This compensating mechanism also'serves the further purpose of modifying the speed of rotation of the ear in accordance with the speed at whie the abrasive screw is fed axially. As-

suming that theabrasive screw is not moved axially, change gears 50 will be so selected that the abrasive screw and ear will be driven at proper relative speedsdcpcnding upon the circular pitch of the teeth on the gear. If, however, the abrasive screw is moved axially, as heretofore described, in order to change or shift the grinding area thereof, then the meshing relation between the abrasive screw and the ear is disturbed,

making it necessary to mo ify the speed of rotation of the car so that it will properly mesh with the a rasive screw. To this end, proper change gears for the compensating mechanism will be selected.

In selecting the proper change gears 51, in order to compensate for the axial movement of the abrasive screw during the grind ing operation, consideration must be given to the fact that, since theabrasive screw is angularly disposed to the grinding plane, the abrasive screw must beshifted at a slightly greater speed than wouldbe'the 'case if its axis were parallel to the grinding plane. This is true because the normal pitch of the thread on the screw, thatis,"thepitch as measured in the grinding plane,"willbe less than the linear pitch, that is, the pitchof the screw as measured on aline parallel toitsaxis- 1 The compensating mechanism, either that indicated by the numeral '51 or additional mechanism in series therewith, "may be em-' ployed to modify the relative speedbetween the abrasive screw-and the, gear. operated upon in accordance with the change of diamcter of the abrasive screw upon repeated truing or resurfacing thereof. It will be observed that when the abrasive screwis resurfaced, the diameter thereof will heremaintaining the same pitch of thread, the angle of lead thereof will be varied. When the diameter is thus reduced, if the same angular speed of the abrasive screw is maintained, the, ear operated upon must be slightly spee ed u tomaintam the proper meshing relation etween this screw and 'duced, and when it is thus reduced, while gear. Also, when the diameter of the abrai sive screw is reduced, thereby changing the angle of lead of thethreadthereon, the axis of the abrasive screw must be angularly adjusted and then the ears of the com nsating mechanism 5 1-w1ll be selected with the statements made in the preceding paragraph in. mind. In practice, it ma not be necessary-to compensate after eac truing operation on the screw. It may be found sufiicient to provide compensating change gears which will take care of the relative speeds between the abrasive screw and gear when the abrasive screw has beenbroug t to predetermined diameters after repeated truing operations.

It may be stated that the compensating mechanism or mechanisms may take any desirable form and, if preferred, a single compensating mechanism havin a sufiicient number of change gears suitably marked for identification, may ,be used to take care of the various reasons or factors why compensation should be had or,if desired, a separate compensating mechanism, such as change gears or a jack-in-the-box, may be provided for taking care of each factor in compensating.

The cam 15, which moves the abrasive screw carriage into and out of operative position, and. the cam 30, which swings the lever 33 to raise and lower the work spindle d, are mounted on a shaft 55 carrying a worm wheel 56 with which meshes a worm 57 on a shaft 58' having on its right hand end a ear wheel 59 meshing with a worm 60 on the constantly driven shaft 45.

The screw 17, by means of which the holder 14 is moved to shift the'abrasive screw axially during the grinding operation, is driven by means of a worm ,63 on shaft 43 and meshing with a worm wheel 64: on the screw. The worm wheel 64L is carried by a bracket'65 extending fromthe holder 14, and

this worm wheel is adapted to be fixed to the screw 17- by means of a clutch sleeve 66 keyed for sliding movement on the screw. During the grinding o eration the clutch, of WlllCll the sleeve 66 orms a part, is engaged, as shown in Figsil and 6, so that the screw 17 is positively driven.' After the grinding operation is completed, the abrasive screw may be moved axiall towards .the right by manually turning t e screw 17 in the correct direction, as by means of a handle positioned on the squared end 67 of the screw. The truing mechanism, as will be hereinafter described more in detail, is

driven and controlled in its movements by suitable shafts connected to the shaft 45.

The machine so far described is set up and operates as follows: The slide 13 is angularly "adjusted, on ,the guide 12 of the carriage ll to such position that the convolutions of the thread on the abrasive screw, where they engage thegear blank, are in proper relation with the teeth on the blank, for instance, in

arallelism therewith. Where a spur gear 18 being ground, the angular adjustment is such that those portions. of the convolutions of the thread on the abrasive screw adjacent the gear blank are vertical, as shown in Fig. 1. If a spiral toothed gear is being ground, then the abrasive screw will be adjusted so that the convolutions thereon are inclined in accordance with the angle of the teeth on the gear. The proper change gears 50 will be selected in accordance with the oi rcular pitch of the teeth on the gear, and the change gears of the compensating mechanism 51 will be so selected as to compensate for the axial movement of the abrasive screw consideration.

being given to the angularity of the abrasive screw. Where a spiral toothed gear is to be operated upon, these latter gears 51 will also be selected in accord with the angularity of the teeth on the gear blank. Assuming that the gear to be ground has been properly positioned upon the work spindle, so that the teeth on the gear will mesh with the thread on the abrasive screw, and other parts have been properly adjusted, the grinding operation is proceeded with. During the grinding operation the abrasive screw and gear blank will be continuously rotated, the gear will be raised by the cam 30 so that the teeth thereon will be ground throughout their length, and the abrasive screw will be shifted axially so as to change the grinding area thereon. After the grinding operation has been completed, at which time the gear will have reached a point above the grinding plane, the cam 15 will come into play to move the carriage 11 backwardly, thereby withdrawing the abrasive screw, and then the cam 30 will have reached a point where the work spindle is free to drop on its return stroke. When the thread on the abrasive screw has become out of shape, it is retrued in the manner hereinafter described and. then moved forwardly into operative position. When the abrasive screw has been trued to such an extent that its diameter wardly of the abrasive screw, is a supporting slide adapted to be moved longitudinally of the abrasive screw by meansof a lead screw 76. Mounted on the. supporting slide 75 for movement trans\-'ersel y of the abrasive screw is across slide77 on which is a longitudinally adjustable supplementary slide- 78. On this latter slide is a turn table 79 rotatable about. a vertical axis and carrying on its upper-face a slide 8() adjustable on a line normal to the axis of the table. 79. This slide may be kttljtR-itml in any suitable manner, asby means of a screw 81. The slide 80 carries the surfacing tool which is here shown, for-illustrative purposes, as being in the form of a diamond point 82. The lead screw 76, by means of which the truing mechanism, as a whole, is reciprocated in the direction of the axis of the abrasive screw, is driven from the shaft 45 through the spiral gears (see Fig. 1), shaft 86, reversing mechanism shown in Fig. 4, shaft 87, and the train of change gears 88 connecting this shaft to the lead screw, as shown in Fig. 3. The reversing mechanism may be of any suitable construction. In the present instance, the shafts 86 and 87 are in alinement with each other, and'splined on the shaft 86 is a clutch sleeve 89 having a. single clutch tooth at each end. When the clutch sleeve. is moved to the right, referring to Fig. 4, it fixes a normally loose gear 90 to the shaft 86, whereupon the shaft 87 is driven in one direction through the gears 90, 91, 92, 93, and 94, the latter gear being fixed on the inner end of the shaft 87. When the clutch sleeve 89 is moved to the extreme left The shipper lever may be moved to neutral position, when it is desired to throw the truing mechanism out of operation, by moving the handle or rod 97 to proper position. In order that the resurfacing tool will be clear of the abrasive screw upon the reverse stroke of the support 75, the cross slide 77, together with the parts carried thereby, are moved bzwkwardly by a cam 100 splined on a shaft. 101 and slidably supported thereon by a bracket 102 forming part of the supporting slide 75. Pivoted in this bracket, as at 103, is a lever 104, one end of which rides upon the periphery of the cam 100 and the other end of which engages a depending lug 105011 the cross slide 77. The cross slide 77 is normally urged in a direction towards the abrasive screw by a spring 106 carried by the supporting slide 75 and acting through a plunger 107 pressmg against the cross slide 77. The cam 100 is of such construction and is driven at such speed that, after completed an operative stroke, the cam will throw the lever 104 in a direction to withdraw the cross slide away from the abrasive screw and hold the same in such position during the reverse stroke of the truing mechanism. \Vhen the truing mechanism has completed its reverse stroke, thecam 100 is in such angular position that the spring 106 may move the'cross slide and the resurfacing tool carried thereby forwardly so that the latter will engage the thread on the abrasive screw during the next operative stroke of the truing mechanism. I The shaft 101 is driven in any suitable manner in timed relation to the reversing mechanism for the lead screw 76. In the present instance, this shaft is driven from a worm 109 through change gears 110 (see Fig. 2). It will be seen that the truing mechanism is shown more or less diagrammatically, it being understood that the construction is shown by way of example only.

The operation of the truing mechanism is briefly as follows: When the abrasive screw has become worn to such an extent that it should be retrued, the slide'13 is adjusted on the guide 12 so that the axis of the abrasive screw and theline on which the resurfacing tool or diamond point 82 is reciprocated during the resurfacing operation are in parallelism with each other. The abrasive screw is withdrawn rearwardly to bring it into operative position relative to the diamond point by means ofthe screw 16.

Suit-able change gears 88 will be selected for moving the truing device longitudinally of the abrasive screw in accordance with the pitch of the thread thereon. The dogs 96 will be properly set on the supporting slide 75 so as to correctly, control the reciprocating movement of the truing device. Also, suitable change gears 110 will be selected for rotating the cam 100 in proper timed relation to the reciprocating movement of the truing device. The table 79 will be angularly adjusted in accordance with the angularity of one side face of the thread on the abrasive screw. This table may be secured in any predetermined angular position of adjustment by T-bolts 112, the heads of which work in an annular T-groove 111 in the upper face of the supplemental slide -78. The slide 80 is then'manually advanced to bring the diamond point between the conrelations of the thread on the abrasive screw. and then the supplemental slide 78, together with the parts carried thereby, are

adjusted longitudinally, as by means of ascrew 7 8' to accurately bring the diamond point into engagement with the selected side the resurfacing tool has face of the thread on the abrasive screw. After the parts have thus been properly adjusted,'the reversing mechanism shown in Fig. 4 is thrown into operation, whereupon it may be assumed that the lead screw 76 is rotated iii a direction to move the truing mechanism on its operativestroke. During this stroke the diamond point will be moved longitudinally in accordance with thepitch of the thread on the abrasive screw, thereby taking a cut, say on the outer edge of the face of the abrasive thread operated upon. When the diamond point has moved. past the end of the abrasive screw, the diamond point will be withdrawn by the cam 100, the reversing mechanism will be thrown by one of the dogs 96 causing the lead screw 76 to rotate in a direction to move the truing mechanism on its return stroke. During this reverse stroke, the diamond point slide 80 may be manually advanced a very slight distance so that on the next operative stroke of. the truing mechanism it will take another cut in the face of the thread on the abrasive screw. 'When the truing. mechanism reaches the end of its reverse 'stroke, the cam 100 will have come in such position that the spring 106 will move the cross slide, together with the diamond carried thereby, forwardly into operative position, and then the reversing mechanismis again .thrown by the other dog 96 so as to rotate the lead screw in a direction to move the truing mechanism on its operative stroke. This sequence of movement is repeated until one face of the thread is properly resurfaced throughout its depth, it being understood that between the suc cessive operative strokes of the diamond point the diamond point is advanced slightly so as to take successive cuts on the face of the thread operated upon. After one face of the abrasive screw is properly resurfaced, the table 79 will be angularly adjusted in accordance with the angularity of the otherfaee of the abrasive'thread, that 'is to say, this table will be so adjustedthat- 'the line on which the carriage 80 is adjusted will be in parallelism with the face of the thread on the abrasive screw to be operated upon, as shown by dotted lines, Fig. 7 It will be observed that the line on which the abrasive screw is resurfaced is in parallelism with the axis of the abrasive screw, but the line on which the abrasive screw contacts with the gear to be ground is at an angle to the axis of the abrasive screw; therefore, in resurfacing the abrasive screw the truing device will be so set and moved to take care lie of the fact that the angles of the faces of I the thread on a line in parallelism with the axis of the abrasive screw is slightly different from the angle of the faces of the thread inthe grinding plane.

In Fig. 8, I have shown diagrammatically an arrangement of truing mechanism which may be employed to advantage when it is desired to true an abrasive serew having a thread with its sidefaces other than straight in the direction of their depth. In this ligure, I have shown an abrasive screw having athread with double curve faces so that the abrasive screw, in outline, will correparticulars to the shape to be given to the side faces of the thread on the abrasive screw. The slide 80 is provided with projections 126 which engage and follow the-curved faces on the cams 125. The slide 80 is urged in a direction to maintain it in proper engagement with the cams 125 in any suitable manner, as by means of spring pressed plungers 127. The diamond slide 80 is moved transversely of the abrasive screw by a screw 81 fixed against longitudinal movement relative to the slide 80 and cooperating with a but 128. The slide 80 has an elongated opening 129 receiving the screw 81 so as to permit of lateral movement of the slide. It will be understood that, with the arrangement-just described, the diamond point, after each operative stroke longitudinally of the abrasive screw, will be fed sli htly inwardly towards the axis of the screw by turning the screw 81, and when the diamond point is thus fed inwardly, it is moved slightly longitudinally of the abrasive screw, owing to the cams or patterns 125. When one side face of the thread on the abrasive screw has been trued up in the manner just described, the pattern cams 125 are reversed and inverted so that thecarn surfaces thereon will take the dotted line position shown in these figures. The other side face of the thread on the. abrasive screw may then be rctrued. 'lhe cams 125 are diagrammatically shown as being held in position by suitable studs 130 and lugs 131.

As many changes could be made in the above construction and many apparently ing sense.

It is also to be understood that the language used in the following claims is in- 79* is the turn table having on tended to cover all of the generic and specific features of the invention herein. described and all statements of the scope of the invention which, as a matter of languge, might be said to fall thei'cbetwecn.

that I claim is 1. In a machine for grinding toothed gears, an abrasive serew having a thread of uniform outside and root diameters and corresponding in pitch to the circular pitch of the gear to be ground and'uniformly corresponding inv normal cross section to a rack tooth adapted to properly mesh with the, teeth of the gear to be'ground, means for rotatabl y supporting the toothed gear to be operated upon, and means "for driving said abrasive screw and said supporting means, said abrasive serew being mounted for angular adjustment about a line normal to its axis whereby the convolutions on theabrasivc screw where they engage the car will be in proper relation to the tecti of the gear; I

2. In a machine for grinding toothed gears, a rotary abrasive screw having a thread adapted to mesh with and have a generating action on the the teeth of the gear to be ground, means for driving said abrasive screw and the gear in timed relation,

.means for advancing said gear axially dur.

ing the grinding operation and then returning it, and means for moving the abrasive screw out of operative position to permit of the return stroke of said gear.

3. In a machine for grinding toothed gears, an abrasive-screw having a grinding thread, a work support, means for movingthe work support axially, and mechanism for drivmg said abrasive screw and work support in timed relation and including means to. modify the relative speeds of the abrasive screw and support in accordance with the angularity of the teeth on the work.

4. In a machine for grinding toothed gears, a tool spindle and a rotary work support. disposed generally at right angles to one another, an abrasive screw on said spindle having a thread, the pitch of which corresponds to the pitch of the teeth on the gear to be ground, means for axially moving said work support during rotation thereof, and means for driving said spindle and support in such timed relation to one another that the eonvolutions of the thread on the abrasive serew will mesh with and generate the teeth on the gear throughout the grinding operation.

5. In a machine for grinding toothed gears, a grinding element comprising an abrasive screw having a thread uniform throughout its length and adapted to mesh with and generate the teeth of a gear, a work supporting element adapted to support the gear with its teeth meshing with said thread. said thread havinga larger number of convolutions than the number of teeth engaged by the thread when in mesh with the gear, and-means for rotating said abrasive screw and supporting element in timed relation, one'of said elements being movable during the grinding operationrelative to the other and without changing the operative relation between said elements to change the grinding areas on the abrasive screw and thereby distribute wear thereon.

6. In a machine for grinding toothed gears, a grinding element comprising an iLbIfiSlVG, screw, the thread of which corre-- sponds in cross section and pitch to a rack com )lementary to the gear to be ground, the num er of convolutions of said thread being such that at any time during the grinding operation at least one cdnvolution is out of engagement with the work, a work supporting element with its axis disposed at an angle to that of the abrasive screw, means for rotating said abrasive screw and work supporting element in timed relation to generate the teeth on the gear being ground, and means for moving one of said elements relative to the other to change the grinding areas on the abrasive screw to distribute wear thereon without disturbing the operative relation between the abrasive screw and the gear.

7. In a machine for grinding toothed gears, a grinding elementfcomprising an abrasive screw, the thread of which corresponds in the grinding plane in cross section and pitch to a rack complementary to the gear to be ground, said thread being of uniform shape, pitch, outside diameter and root diameter throughout its length, a work supporting element with its axis disposed at an angle to that of the abrasive screw, means for rotating said abrasive screw and work supporting element in timed relation to generate the teeth on the gear being ground, and means for uniformly moving in a single ation one of said elements relative to the other and generally longitudinally of the axis of the screw to change the grinding areas on the abrasive screw and thereby dis-- tribute wear thereon while maintaining the same grinding plane.

8. In afimachine for: grinding toothed gears a. grinding element-comprising anabrasive screw, an element for supporting a member with its teeth in mesh with the thread of said abrasive screw, the thread of said abrasive screw having a greater number. of convolutions than are in engagement with said member dur ng the grinding operatlon,

9. In a machine for grinding toothed gears, a grinding element comprising an abrasive screw having a thread of uniform pitch, outside diameter and root diameter throughout its length, an element for supportinoa toothed gear with its teeth in mesh with the thread on the abrasive screw, a device for moving said abrasive screw axially in a single direction during the grinding operation to change the grinding areas of said screw to distribute wear thereon, and

means for driving said element and device in timed relation.

10. In a machine for grinding toothed gears, a grinding element comprising an abrasive screw, an element adapted to support a gear with its teeth in mesh with the thread on said abrasive screw, means for moving one of said elements relative to the other: axially of said screw and in a single direction to change the grinding area on the abrasive screw and thereby distribute wear thereon, and mechanism for driving said abrasive screw and work supporting element intimed relation and including means for compensating for said relative movement between said elements,

- 11. In a machine for grinding toothed gears, a grinding element comprising an abrasive screw, the thread of which -is adapted to mesh with the teeth of the gear to be ground, said screw havinga longer thread than is necessary to mesh with the gear being ground, said abrasive screw being mounted for angular adjustment in accordance with the lead angle of the thread thereon, a rotary work supporting element, one of said elements being movable relative to the Other in" the longitudinal direction of the abrasive screw to change the grinding area of, the latter and thereby distribute wear thereon, and means for driving said ele- "ments. direction and throughout the grinding oper- 12. In- 'a machine for grinding toothed gears, an abrasive screw having a thread uniform throughout its length and mounted foran'gular-"adjustment about a center lying in its-axis and for axial movement, a rotary work'support, and means for driving said abrasive screw and support in timed relation.

13. 'In as. machine for grinding toothed gears, arotatable work support, an abrasive screw having a thread adapted to mesh with the teeth on the work, a holder for said abrasive, screw adjustable about a center lying: in the axis thereof, means for axially moving said holder and abrasive screw during the grinding operation, whereby wear on said screw is distributed, and means for rotating said abrasive screw and supportin timed relation,

14. In a machine for grinding toothed gears, a grinding element comprising an abrasive screw having a thread corresponding in itch and cross-section to a recliners-- plemcntary to the gear to be ground, a work supporting clement disposed at an le to the axis of said abrasive screw, one 0 said elements being movable relative to the other longitudinally of the work supporting element whereby the gear is traversed across the abrasive screw, one of said elements being movable relative to the other longitudinally of the abrasive screw to cha e the grinding areas thereon andthereby distribute wear, and means for driving said elements in timed relation.

15. In a machine for inding toothed gears, an abrasive screw aving a thread adapted to mesh with the teeth of the gear to be ground, said screw being of such length that when in meshing relation of the'screw with the gear being ground one or more convolutions of the screw is out of engagement with the gear, a rotary work support, means for moving said support axially to traverse the gear across the abrasive screw, means for moving said abrasive screw axially to change the grinding areas thereon and thereby distribute wear, and means for driv ing said mentioned means, abrasive screw and support in timed relation.

16. In a machine for grinding toothed gears, an abrasive screw having aspiral thread adapted to mesh with the teeth of the gear to-be ground, a rotary work su )ort means for movin said su ort axia to traverse the gear across the abrasive screw, means for moving said abrasive screw axially to change the grinding areas thereon and thereby distribute wear, and means for driving both of said moving means, said abrasive screw and said support in timed relation, said driving mechanism including means for modifying the relative rotation of the abrasive screw and support in accordance with the angularity of the teeth on the ear. g 17. In a machine for grinding toothed gears a grinding element comprising an abraslve screw having a thread corresponding in pitch and cross-section to a rack complementary to the gear to be ground, a work supporting the axis 0 said abrasive screw, said abrasive screw being angularly adjustable, one of said elements being movable relative to the other longitudinally of the work supporting ele ment whereby the gear is traversed across the abrasive screw, one of said elements being movable relative to the other longitudinally of the abrasive screw to change the grinding areas thereon and thereby distribute wear, and means for driving said elements in: timed relation. p v

18. In a machine for grinding toothed gears, an abrasive screw having a thread adapted to mesh with the teeth of the gear to be ground; a rotary work support, said abrasive screw being angularly adjustable element disposed at an angle to mentioned means, abrasive screw, and support in timed relation.

19. In a machine for rinding toothed gears, an abrasivelscrew aving a thread adapted to mesh with the teeth of the gear to be ground, a rotary work support, a device for transverselfy moving said abrasive screw into and out o operative position relative to the work, a device for moving said work su port axially to traverse the gear across the abrasive screw and then return it, and means for driving said devices, abrasive screw and support in timed relation.

20. In a machine for grinding toothed gears, an abrasive screw having a thread to mesh with the teeth of the gear .to be ground, a rotary worksupport, means for moving said support axially to traverse the gear across the abrasive screw and then return it, means for moving said abrasive screw axially to change the grinding areas thereon and thereby distribute wear, means for moving said abrasive screw transversely to permit the gear operated uponto clear the abrasive screw on the return stroke of said support, and means for driving the parts in timed relation.

21. In a machine for grinding toothedmesh with the teeth of the gear to be ground, said abrasive screw being angularly adjustable abouta line normal to its axis, a rotary work support, means for moving said support axially to traverse the gear across the abrasive screw and then return it, means for moving said abrasive screw axially to change the grinding areas thereon and thereby distribute wear, means for moving said abrasive screw transversely to permit the gear operated upon to clear the abrasive screw on the return stroke of said support, and means for driving the parts in timed relation.

22. In a machine for grinding toothed gears, a grinding element comprising an abrasive'screw, an element adapted to su port a gear with its teeth in mesh with t e thread on said abrasive screw, said abrasive screw being angularly adjustable to bring the convolutions thereon 1nto proper relation' to the gear, means for moving one of said elements relative to the other to change the grinding area on the abrasive screw to distribute wear thereon, and mechanism for 23. In a machine for rinding toothed gears, an abrasive screw iaving a thread uniform throughout its length and mounted for angular ad ustment about a center lying in its axis and for axial movement, a rotary work support, means for driving said 'abra-' sive screw and support in timed relation, and including means for compensating for such axial movement of said screw' as measured on a l ne normal to the convolutions thereon.

24. In a machine for grinding toothed gears, an abrasive screw, the thread of which corresponds in outline in the grinding plane to a rack complementary to the gear 0 erated upon, a support for carrying the toot i'ed gear to be ground, and means for driving ,said abrasive screw and support in timed relation, including means for modifying the relative speed therebetween in accordance with changed conditions of the abrasive screw upon retruing thereof. J

25. The method of inding toothed gears, which includes rotatlng an abrasive screw having a thread of uniform shape, pitch, outside diameter and root diameter throughout its length in timed and meshing relation with the teeth of the gear'operated upon, and movin said screw axially in a single direction throughout the grinding operation to distribute the wear on the screw.

26. The method of grinding toothed gears, which includes angularly adjusting an abrasive screw to bring the convolutions of the thread thereon in alinement with the teeth of the gear operated upon, rotating the abrasive screw and toothed gear in timed relation, and continually bringing new additional grinding portionsof the screw into engagement with the gear by relatively moving one of the elements axially ofthescrew during the grinding operation.

27. The method of rinding toothed gears, which includes rotatmg in timed relation the ear to be ground and an abrasive screw having a thread, and axially moving the abrasive screw continuously in a' single direction during the grinding operation while maintaining the same operative relation between the abrasive screw and gear to thenby bring additional grinding areas of said thread into operation and thus distribute the wear on said thread.

28. The method of grinding toothed gears, which includes rotating an abrasive screw in timed relation with the toothed gear to be ground with the thread of the screw meshing with the teeth of the gear, relatively moving one of the elements axially of the gear to traverse the gear across the abrasive screw, and relatively moving one of said elements continously in a single direction during the grinding operation axially of the abrasive screw to shift the grinding area thereon and thereby distribute wear upon said thread.

BENGT M. W. HANSON. 

